It’s very strange. I’ve not modified any codes to my knowledge. I’m not a programmer. So prior customizations would have been done on the previous theme I was using. I can only remember changing the text of my 404 error page in the past before loading Full Frame.
I forgot to mention in my first post that when in the customizer I am not able to see the preview at all. Only a spinning icon as if the page is trying to refresh is seen no matter which option I am trying to view. So the only way I can see if any changes are to my liking is to save and publish, then refresh a live version of my site in another tab.
I disabled all plug-ins as you suggested. It was only then that I was able to see another section of the Featured Content options and I changed the default background and the headline. I was not able to get any options to change the Featured Page to use the 3/4 selections that are supposed to be possible. So I disabled it from showing the default instead. I tried looking for it in other areas of the customizer and to see if I could change the Featured Slider. Nothing new could be found anywhere else.
Returning to the Featured Content area of the customizer I tried refreshing my browser hoping that my preview would show up. Then the options to modify the Featured Content I was finally seeing before disappeared again. I am left only with the new background and headline I changed before this option disappeared. Thankfully I am happy with this much for now. However, I would like to put in the featured page info of linking to different services I want to showcase.
Thinking that perhaps it was a corrupted install of the theme, I also downloaded a new copy and reinstalled it. Nothing new. I’ve turned back on my plugins and will go back to adding more content on other pages for now.